WARSAW, Sept 17 (Reuters) - Poland's Energa has suspended plans to build a 1000-megawatt coal-fired unit in the country's north-east due to problems securing financing and will instead invest in the power grid, gas-fired generation and renewables, the utility said on Monday.

Poland's fourth-largest utility also said that by 2020 it plans to have capacity of around 2550 MW, of which some 1000 MW would be gas-fired, 900 MW would come from renewables, around 450 MW from coal and 200 MW from co-generation units.

The utility expects to spend around 25 billion zlotys ($8.1 billion) through the end of the decade, with half going toward investments in the power distribution network.

"Contrary to what is believed, slower than planned construction of new generation is not the main threat to the security of Poland's power system," Energa Chief Executive Miroslaw Bielinski said in a statement.

"The risks to the system's stability and its development come from the bad condition of the grid."

Energa suspended the investment in Ostroleka because of problems with acquiring financing and what it called an unfavourable situation in the country's construction sector. The utility will now seek a partner for the project.

Local utilities are looking to invest an estimated 100 billion zlotys or more by 2020 to replace Poland's outdated power plants and to create new sources of energy for its economy, which has avoided recession throughout the financial crisis and in the subsequent euro zone debt crisis.

State-controlled utilities PGE, Tauron, Enea and Energa all have ambitious for long-term investment plans that collectively run into billions of U.S. dollars.

Other state-led companies such as refiner PKN Orlen , gas monopoly PGNiG and copper miner KGHM are also seeking to invest in power generation to become less dependent on utilities and to generate new sources of revenue.